MOTIVATION: Taverna workbench is an environment for construction, visualization and execution of bioinformatic workflows that integrates specialized tools available on the Internet. It already supports major bioinformatics services and is constantly gaining popularity. However, its user interface requires considerable effort to learn, and sometimes requires programming or scripting experience from its users. We have integrated Taverna with OpenOffice Calc, making the functions of the scientific workflow system available in the spreadsheet. In CalcTav, one can define workflows using the spreadsheet interface and analyze the results using the spreadsheet toolset. RESULTS: Technically, CalcTav is a plugin for OpenOffice Calc, which provides the functionality of Taverna available in the form of spreadsheet functions. Even basic familiarity with spreadsheets already suffices to define and use spreadsheet workflows with Taverna services. The data processed by the Taverna components is automatically transferred to and from spreadsheet cells, so all the visualization and data analysis tools of OpenOffice Calc are available to the workflow creator within one, consistent user interface. AVAILABILITY: CalcTav is available under GPLv2 from http://code.google.com/p/calctav/ CONTACT: [email protected].